Equalizing hydraulic ram travel



May 29, 1945.

J. HESS EQUALIZ ING HYDRAULIC HAM TRAVEL Filed Sept. 29, "1941 3 Sheets-Sheet 1 an/aw @wyww 3 Sheets-Sheet May 29, 1945. R. J. HESS I EQUALIZING HYDRAULIC RAM TRAVEL Filed se i. 29, 1941 l l l I I 4 l l I J wlllrllllltllll /l May 29 1945. J HESS 2,377,007

EQUALIZING HYDRAULIC RAM TRAVEL Filed se tgzs, 1941 s Sheets-Sheet a Patented May 29, 19 45 UNITED STATES PATENT OFFICE EQUALIZING HYDRAULIC RAM TRAVEL Relza J. Hess, Park Ridge, 111., assignor; by mesne assignments, to American Steel Foundries, a

corporation of New Jersey Application September 29, 1941, serial No- 412,819

4 Claims.

The present invention, relates to hydraulic presses and particularly to means for controlling and equalizing. the travel of two or more. spaced rams that may be applied to advance the platen of the press.

The problem of causing equal advance of spaced portions. of a platen drivenby spaced rams under hydraulic pressure has. caused many difiiculties in th past. Many methods of operation and mechanisms of many types have been tried as a means of solving this problem. The various solutions of which I am aware are not practical in all instances. In some cases it is because of lack. of accuracy. In other cases too many delicate parts.

are necessary while inmost cases the solution of the problem requires complicated and expensive mechanisms. where wearof the parts soon makes them incapable of. performing the desired function.

The present invention contemplates means for.

equalizing the travel of two spaced rams, which means embodies a simple valve and control lever arrangement whereby fluid from a source under pressure is. so fed to the spaced rams that any tendency of one ram to get ahead of the other is; immediately and directly offset by 2, corresponding reduction in the quantity of fluid directed toward that ram. Moreover the present invention contemplates a means of this characterwherein the change in the proportion of, fluid directed to any change whatsoever in the capacity of: the valve.v In accordance with the Present invention it is also contemplated that the control of the advance of. one ram'a-head of the other is increasingly sensitive and effective-as the rams approach their final advanced position.

Other and more specific oiects and advantages of the present invention will appear from the following description, reference beinghad to the accompanying drawings whereina preferred form of the. invention is shown. It is tobe. understood; however that thedrawings and description are illustrative only and are not to be taken as limitthe two rams is accomplished without effecting Fig. 4 isan enlarged detailed view illustrating the control mechanism and its: connection to the valve Fig. 5 is-a sectional view taken onthe line 5-5 of Fig. 1; a V

Fig, 6. is a fragmentary plan view of part of the mechanism shown in Fig. 4-,;

Referring now in detail to the drawings, the present invention is shown in- Fig.1 as embodied in a press such as, a bending or shearingpress 4, the bed plate of which: isindicated at 5 and the moving platen of which is indicated at 6-. The

moving platen 6 is movable vertically downward by means: oitwo hydraulic-rams l and 8 housed in cylinders Band II). The moving platen 6- is lifted by means of pull-back rams- II and 12' housed in cylinders t3 and I4, these rams being connected by rods I5. and L6 to the platen. The rams are actuated by fluid under pressure which is pumped by means of a pump II froma tank I8, the pump l-l being driven bya motor I9. The pressure liquid is fed through a relief valve 20 to a 4-way control valve 2 lwhich may be controlled by any suitable means, manual-or automatic, alternatively tol directxfiuid under pressure to one of two.- supply pipes 22- and'23. The supply pipe 22- directs the liquid under pressure through a control unit 24 to the cylinders 9 and Ill to thus. advance the: rams 1- and 8, The supplypipe 2-3 directs, the liquidunder pressurethrough a holding. valve 21- to. the cylinders I3' and [4 so as to lift the rams- I l and [2 for withdrawing the movable platen '6;

As illustratedthe control unit 24 is connected by pipes 25. and 26 to thecylinders Sand in, re-

spectively. Suitable quick exhaust valves 28 and 29are provided in. the pipes 25 and 26; these valvesbeing adapted to provide an exhaust outlet back to. the tank I8 toexhaust the fluid from the cylinders 9 and I0 when the platen 6 is being raised. after an advance; stroke. The valves 28 and 29 as shown. are connected to the supply pipe 23. so. as to. be actuatedby fluid from the pipe 23.

The control unit. 24,. is illustrated more completely in Fig, 3. This is. adapted to direct, fluid from an inlet 30.110 one of two outlets 31., 32-. The

outlet,3 l. leads,to the pipe 26, while the; outlet 32, leads to the pipe 25-. The unit 24' is a. balanced:

valve. construction comprising a casing 33* having 36 and 3! extend into enlarged outlet portions 40 and 4| of the chamber. The valve 35 has a reduced portion 42 between the cylindrical portions 36 and 31. The portions 36 and 3'! and the reduced portion 34 of the chamber are machined to give an accurate fit. Also, the portions 38 and 31 are in normal position when the two ends of the platen 6 are even. In their normal position the portions 33 and 3'! are equally spaced from the adjacent edges of the reduced portion 34.

The portions 36 and 37 are so spaced apart that when the valve is moved to the right or left the total opening provided is substantially the same from the point where one of the enlarged portions 3'! completely cuts ofi its outlet to the point where the other enlarged portion 36 completely cuts oil its outlet. I make use of this characteristic of the valve construction to obtain a smoothly operating correction of any tendency of one ram to advance faster than the other. Mechanism is provided to move the valve 35 instantly and in proportion to any advance of one ram ahead of the other. of the other for any reason, the moving platen tips slightly and this tipping is translated into a direct movement of the valve 35 in a direction to increase the size of the outlet to the cylinder for the rain that is lagging behind. Immediately the available flow of liquid is diverted more to the cylinder of the lagging ram and less to the cylinder of the leading ram until the tipping is corrected. Furthermore, with the mechanism provided the correction in the size of outlet opening becomes increasingly or decreasingly sensitive as the movable platen approaches the limits of its travel,

The particular mechanism for controlling the movement of the valve 35 in response to tipping of the moving platen comprises a stem 43 on the valve having threads 44 on the end thereof. The stem 43 is threaded into a slotted block 45. The other end of the block 45 is provided with a reduced extension 46 sliding in a bearing 41. The block 45 is slotted at 48 to receive a bar 49 that is fixed to the moving platen 6. A cover plate 50 (Fig. 6) holds the bar 49 in the slot 48. Within the slot 48 two knife edge bearings and 52 are provided for the bar 49. The bearing 52 is a spring pressed pin having a key 53 thereon to prevent it from turning. A spring 54 holds'the bearing snugly against the bar with sufficient force to cause the block 45 to move endwise in response to any angular movement of the bar 49, The bar 49 however may slide vertically in the block 45 between the bearings 5| and 52. The parts are machined accurately to eliminate any lost motion between the bar 49 and the block 45. As

the moving platen is lowered the valve stem 43 is caused to move further for a given angular movement of the moving platen because of the increase in effective length of the bar 49.

With the apparatus hereinbefore described a positive and accurate equalization of the travel of two spaced rams is obtained. Provision is made in the connection of the stem 43 to the block 45 for adjustment of the valve position with respect to the platen position. This is done by threading the stem into the block 45. The construction is such that the valv openings between the inner ends of the portions 36 and 31 and the adjacent edges of the portion 34 can be made equal when the platen is level to a very accurate degree. The valve 35 is balanced in all positions. The end of the bore 38 is open through a port 55 to the tank 18. A passage 56 connects the bore 39 with the Thus if one ram gets slightly ahead bore 38. A seal 51 is provided to prevent leakage around the stem 43.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a hydraulic press wherein there i provided a platen and a ram disposed at each side of the center of the platen to which pressure fluid is applied for causing the platen to travel, a source of fluid under pressure for supplying pressure fluid to said rams, and valve means responsive to uneven travel of said platen to change the proportion of valve opening for fluid to the rams, said valve means comprising a valve casing having a chamber comprising an inlet chamber, two outlet chambers, each connected to one of said rams, a balanced valve in said chamber having two valve portions each controlling flow from the inlet chamber to one of said outlet chambers, said portions being movable together to restrict one outlet as much as the other outlet is opened, and valve moving means, operable upon advance of one ram ahead of the other, to shift said valve in a direction to restrict the outlet to the leading ram and increase the outlet to the trailing ram, said valve moving means comprising a block having a slot, said block being slidably mounted on the press and presenting within said slot an integral knife-edge bearing, a spring pressed pin mounted in said slot and presenting a knife-edge bearing spaced from the firstmentioned bearing, a connection between said block and said valve, and a bar fixed to said platen and extending between said bearings for slidable engagement therewith, said bar having a lever arm increasing in effective length as said platen is advanced by said rams.

2. In an hydraulic press comprising a platen and a plurality of rams disposed at opposite sides of the center of said platen, to which rams pres- .sure fluid is applied for advancing said platen, a

source of fluid under pressure for supplying pressure fluid to said rams, valve means responsive to uneven travel of said platen to change the proportion of valve opening for said fluid to said rams, and valve actuating means comprising a member on the press having a slot therethrough, a block having at one end thereof a portion slidably fitted in said slot, said block having an opening therethrough and presenting within said as said platen is advanced by said rams.

3. In a hydraulic press comprisinga platenand .a plurality of rams disposed at opposite sides of the center of the platen, to which rams pressure fluid is applied for advancing said platen, a source of fluid under pressure for supplying pressure fluid to said rams, valve means responsive to uneven travel of said platen to change the proportion of valve opening for said fluid to said rams, and valve actuating means comprising a block having a slot, said block being slidably mounted on the press and presenting within saidslot an integral knife-edge bearing, a spring-pressed pin mountedin said slot and presenting a knife-edge bearing spaced from the first-mentioned bearing, an operative connection between said block and said valve means, and a bar fixed tosaid platen and extending between said bearings for slidable engagement therewith, said bar having a lever arm increasing in efiective length as said platen is advanced by said rams.

4. In an hydraulic press wherein there is provided a platen and a ram disposed at each side of the center, thereof to which pressure fluid is applied for causing the platen to travel, a source of fluid under pressure for supplying pressure fluid to said rams, and valve means responsive to uneven travel of said platen to change the proportion of valve opening for fluid to the rams, said valve means comprising a valve casing having a chamber comprising an inlet chamber, two outlet chambers each connected to one of said rams, a balanced valve in said chamber having two valve portions each controlling flow from the inlet chamber to one of said outlet chambers, said portions being movable together to restrict one outlet as much as the other outlet is opened, and valve moving means operable upon advance of one ram ahead of the other to shift said valve in a direction to restrict the outlet to the leading ram and increase the outlet to the trailing ram, said valve moving means comprising a block having a slot, said block being slidably mounted at one end thereof on the press and presenting within said slot an integral knife-edge bearing, a spring-pressed pin mounted in said slot and presenting a knife-edge bearing spaced from the first-mentioned bearing, a connection between the opposite end of said block and said valve, and rigid means fixed to said platen and having a lever arm extending between said bearings, for slidable engagement therewith, said lever arm increasing in effective length as said platen is advanced by said rams.

RELZA J. HESS. 

